Freaky Formaldehyde Friday
by MorbidbyDefault
Summary: Birthday prompt from HanHan84: John and Molly are exposed to a strange chemical, causing them to swap bodies for the period of 12 hours. John, now stuck in the small pathologist's form, becomes privy to some previously hidden information: namely the secret relationship between Sherlock and Molly. (Based slightly on parts of Freaky Friday and other comedic movies of the like.)
1. Chapter 1

So, this is a BELATED Birthday prompt for my dear HanHan84, who gives some of the most delightful story ideas, including this gem:

_Molly swaps bodies with john for about 12 hours (no - one knows why, all the two remember before it happened was Sherlock leaving the lab to see Lestrade and on his way out, knocking over a flask of something on the bench. They remembered blackness and woke up as they are now ((body swapped))!) They don't tell Sherlock about it but this is how John discovers their secret relationship._

Teeheehee...I do apologize that it's taken me so long to get this done, my dear, but I hope the contents more than make up for it! Love you, and I hope you had a fantastic birthday!

I hope the rest of you enjoy it as well! Thank you!

**Disclaimer and all: I don't own anything. None of what I do here is for profit. It's a gift for a friend, and I'm just borrowing characters. Also, please don't steal other people's works. Thanks!**

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John sat by idly, watching Molly and Sherlock tag team over the span of the work stations of the lab. He had to admit, even with his experience, both in medical school and the field itself, he would never be as flawless working with Sherlock as Molly Hooper was. He had wondered what changed between the pathologist and detective since Sherlock's near exile. The two had become amiable, Sherlock suddenly making it a point not to spout out his deductions about Molly. She, in return, granted him more access to equipment and corpses than ever before.

A chirp of someone's phone interrupted the veteran's thoughts.

"Yes! Wonderful news! I'll be there right away! Do tell Anderson not to touch anything!" Sherlock pressed his thumb to the screen of his mobile, and pocketed it as he made his way to the door. John stood to join him.

"No, I need you here. Shouldn't be more than ten minutes. John, text me the minute the results of that test are complete. Molly..." John's head snapped to the small woman across the room, spying a shy grin on her face.

"Yes?"

"...Lovely as always." Sherlock was through the door before John could return his widened gaze to him. He missed the way Molly's smile brightened up at Sherlock's words, and he definitely missed the sly wink that the detective gave her in return.

Most importantly perhaps, both of the occupants of the lab missed the shatter-proof flask at the end of the counter falling to the floor. Its mysterious contents slowly dripped onto the floor, while the equally puzzling vapor curled up and lightly sizzled the air molecules overhead.

John had gone back to flipping through a stray copy of the textbook of airborne pathogens, when he heard Molly's the first of Molly's wracking coughs. He was up in an instant, at her side as she hunched over, trying to purchase air in her lungs.

"Molly? What's wrong? Did you inhale something? Come on, stay with me." He could see she was beginning to panic, unable to catch a single breath while her body tried fighting off some foreign intruder. John had stood to rush and get her some water, when a dizzy spell overwhelmed him, sending him immediately onto his backside, eyes flying to a terrified looking pathologist, before darkness took over. The sound of her coughing attacks ebbed into a thick fog, and John felt like he was falling into some of the best and deepest sleep he'd had since being home from the war.

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"_...ly ... Mol... Molly, come on. Wake up! _Molly!?" John opened his eyes as the voice grew stronger, until he was met with the sight of a frantic Sherlock Holmes looming him. He'd half expected a quick slap on the back, or perhaps a shaking of his shoulders, the detective scolding him and telling him to get a grip. Instead, he received a relieved sigh, while strong hands cradled his head. John was about to ask what had gotten into his friend, the bout of sentiment being the rather obvious clue that he wasn't himself. However, as he caught sight of _himself_ lying on the floor just meters away, John's mind quickly halted any conversation he was about to have.

"Are you alright? Don't worry about John, he can handle himself quite well. My main concern is you, Molly," Sherlock gazed over _Molly's_ face, and John stared back at him, deciding that a nod was his best option for reply. Sherlock gave a reaffirming nod, before helping his friend to stand, before making his way to John's body.

_'Oh boy,' _John thought as he watched the man trying to rouse _him_, hoping that Molly would be as quick on her feet in noticing that something was definitely amiss. Namely, them. As Sherlock shook John's body (_'Of course, he'd go for shaking'_), a small whimper rose from his vocal cords.

"Sh-erlock?" John could see Molly's softness reflected in his own eyes, the tired confusion raising the slight wrinkling lines of his forehead. Sherlock was helping him to stand, making sure his, or _Molly's_, balance was alright. In the meantime, Molly was still trying to manage her body (his) to stand, finding the new weight and difference to be a challenge. After a brief scare of watching his own frame tumble back to the floor, he called out to catch her attention.

"Mo... John! Are you alright?" He asked, hearing his voice come out in the soft tone of the pathologist's. John knew right away that she had heard her own voice, and her head darted up to meet his gaze. She squeaked in surprise, producing a rather odd tone from the army doctor's vocal cords. Sherlock looked over to her, his left brow raising ever so slightly.

"John, will you please hurry up and grab the first aid kit? Molly has a cut on her forehead. It needs tending to immediately. Then we can figure out what went wrong in here while I was away." Sherlock shooed the doctor away, and Molly, still confused and staring at herself from across the room, slowly made her way toward the cupboard that held the supplies. John was hoping she would be back soon, so they could begin discussing what happened. However, his thoughts were abandoned, as he felt the consulting detective's lip brush over his _(no...Molly's)_ forehead. He gasped, looking up at Sherlock's concerned features.

"I know...I'm sorry. I just needed to. I'm glad you aren't too much worse for wear. Now, let me see that cut." John looked on as Sherlock examined the slice that had gone over Molly's left eye. It wasn't deep, but by the way Sherlock inspected it, one would suspect it had been a fatal blow to the head. John looked back to his own figure, now approaching with the small kit of gauze and bandages. He caught a sort of bashful glance in his own eyes, and began his pondering on the whole ordeal.

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So, I've decided that instead of doing a one shot of this...I'm going to spread it out over a couple of chapters. :) I hope that's okay with everyone. Anyway, here's the first chapter! YAY! Thanks again for reading, and I hope you'll leave a review to tell me how I'm doing.

Happy BELATED Birthday, to darling HanHan84...I hope I'm doing your idea justice.


	2. Chapter 2

So, here is the second part of this lovely birthday story for my dear HanHan. :) I thank you all for reading the first chapter, and I hope you all enjoy this second part just as much! :D

**PS. It's not mine. I don't own anything. All our rights are belong to...not us. Not our rights. The rights are a lie? um. Yea...basically I'm just writing fanfiction here.**

**Enjoy!**

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Molly brought the kit over, and cautiously met eyes with...herself, trying to wordlessly tell the doctor within that they needed to speak alone. She decided on a plan, one she hoped would work.

"Um...Sherlock?" She asked hesitantly, receiving a hum as an answer.

"I think...maybe we could use some water. I know I could, and I'm sure John...MOLLY! I mean, Molly, could use some water too." She grimaced at her obvious mistake, and tried to play it off, as Sherlock turned to look at his friend. He warily eyed Molly, who gave an encouraging smile. With a sigh, the detective seemed to take the bait.

"Alright, but do try to remain cognitive while I'm gone. Can't have my pathologist and blogger both out of commission," Sherlock said, casually throwing a wink in 'Molly's' direction, who again, looked shocked. As soon as he left the lab, Molly forced John's body to scramble to her own.

"Oh my God. John? What happened to us?!" Her frantic question sounded in a voice not-her-own. Instead, a cracking version of John's echoed in the room. She heard her own voice let out a sigh, one that was entirely too John Watson.

"I don't know, but we have to figure out how this happened, and fast. No offense, but I don't exactly fancy being a woman." Molly let out a huff, before motioning to John's figure, now hers.

"And you think I want this? I just want my own body back. I want to be able to... oh. _Oh, God. _John, I have to tell you something. Sherlock, well we..." Her near confession was cut off by the detective quickly making his way back to their sides, two small glasses of water in his hands. He thrust one into John's calloused fingers, and Molly had to curl away to avoid the splash of cold liquid that cascaded over the lip of the paper cup.

Before she could register what was happening, strong hands were pushing her toward the swinging doors, mumbling on about something to do with 'fresh air' and 'possible concussion'. She heard the latch that bolted the doors fall into its slot on the floor, effectively locking her out. She let out a heavy sigh, wondering what would soon unfold in the darkened lab. She only hoped that Sherlock would behave a _bit_ more than he usually did.

OoOo

Sherlock turned around, having slid the long metal bar down to the groove of the floor. He made his way to Molly's side, taking notice of how startled she looked.

"Are you sure you're alright? You seem...dazed." His voice was so gentle and caring, and John soon found a firm grip on his now slender face. He glanced up, and met the searing look of concern in the detective's normally harsh eyes.

"Sher..." John opened his mouth (no..._NOT_ his mouth) to speak, but found himself being silenced by a set of lips. The kiss itself was tender, filled completely with adoration and the strong sense of, love, for lack of a better word. However, the fact that he wasn't _himself_, and more so, that Molly wasn't _herself_, made such an intimate moment wrong. All this came to mind _before_ the fact that he was currently in a lip lock with Mr. 'Married-to-his-work'. This thought was the one that had him pulling away quicker than lightning strikes.

"Molly? Is something wrong?" Sherlock asked after him, forcing John to concoct the most convincing and convenient lie he could.

"I just...I feel sick. Yea, I feel a bit nauseous. I just need to go home and lie down." John made his way toward the door, letting out an uncertain chuckle as Sherlock pursued.

"Well, I can escort you, ensure that you are alright. I'll even feed that blasted cat of yours." He seemed almost desperate, a side that John had only ever witnessed during his extreme bouts of boredom. Just as Sherlock had him cornered against the door, John successfully opened it, using Molly's heeled shoe to lift the sliding lock out of place. To the innocent bystander, Sherlock in this instance, the pathologist almost looked relieved to see the army doctor still awaiting on the other side.

"Oh, John! You're still here. _Wonderful._" Sherlock sneered, his voice rife with sardonic disdain.

"Well, well yes. I just um... I wanted to make sure...Molly, was alright. Sherlock, maybe you should go hail a cab for her?" John's voice hesitantly offered up the idea. Recognition flashed behind Molly's brown eyes, and she too, jumped to encourage the suggestion.

"Oh, yes! That would be so kind of you. If you could go get...M..._me_ a cab home. I'll just wait here with John, so nothing happens. Um, yea. That would be great. Thanks!" Sherlock seemed to pause as he listened to the two speak, an odd expression lighting his ethereal face. Finally, he bent to the idea, though the narrowing of his gaze told both John and Molly that the gears in that genius mind were turning out a great number of possible explanations.

"Fine, but I will insist upon making sure you are properly settled at home." Without waiting for any potential arguments, he made his way toward the exit, giving the two mixed up souls a moment to talk.

"Molly, how long has Sherlock been snogging you senseless?" The hurried question was the first out of John's borrowed lips. Molly looked positively mortified, taking the form of a bright red hue to John's cheeks.

"Since after he came back from that exile. After your wedding, once, and once right after...the fall." Molly's eyes widened, before John started laughing. The meek woman's giggle fueled the doctor's amusement.

"Well, who'd have ever thought?" He chose the next moment to steel his emotions, and focus on their obvious problem.

"Well, we now have two issues. Sherlock doesn't know about _this_," he motioned between the two of them, "and he doesn't know that I'm now _very_ aware of the two of you. Sorry Molls, but I don't think I could even fake having an _affection_ for him. Best friend or not, he _will_ figure out that something is wrong, and he'll be bloody well pissed if we didn't let him know about the potential for some freak experiment he could do. We need to tell him, so he can help sort us out." John knew he was right, and knew that Molly agreed. She nodded her head, well, his head, just as the consulting genius rounded the corner.

"Right, Molly? The cab is waiting. John? I'll see you later." He seemed to smile at John, giving a stiff nod in his direction. He then pulled Molly's small body after his own, leaving before either could speak. A quiet John, or Molly, stood by herself.

"Good luck getting a chance to do that, John," She muttered to herself.

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Well, this is going to just be completely interesting. Thank you for reading this chapter! One more to go! I hope you'll all join me again for the end! Please let me know what you think! Love you all so much, and I'll meet you next chapter!


	3. Chapter 3

Well, here we are; the final chapter has arrived. I want to say thank you to all of you who have been reading and keeping up on this story. It is short, but it was so much fun to write. A big shout out and thank you to HanHan84, for requesting this plot. It's truly a brilliant and hilarious idea, and I'm honored that you entrusted it to me. I hope it has been acceptable, and again, happy belated birthday!

**I still don't own anything. Dang. Gotta get in on this ownership somehow. :P All the owns are belong to other people.**

**Enjoy!**

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The cab made its way from the hospital, snaking through the busy streets of the city. The air was stale, and John was slightly afraid to breathe it in, for a slightly different reason than one would believe. Sherlock had seemingly pressed himself close to his side, an arm wrapped around Molly's thin shoulders. Breathing would only close the gap more, something John certainly wasn't about to do.

All too soon, they arrived, and Sherlock helped his pathologist (and best friend) out of the car. It was only when they stepped toward the large building, that John realized he had absolutely no idea which flat was Molly's. It didn't really matter, however, as Sherlock placed a hand on the small of his temporary back. He seemed to know exactly where to go, which only served to worry John more. They strolled down one hallway, then another, until finally, they reached the correct doorway they needed. The bright 'Welcome' mat on the floor was indication enough to the army doctor that it was definitely Molly's place.

Sherlock stood by for a moment, watching expectantly. When John made no motion to find a key, the detective produced one from his pocket, sliding it easily into the dead bolt of the door. Any shock that may have previously diminished came flooding back.

"Now, you seem to still be flustered about earlier. What do you need?" Sherlock asked, a small, nearly coy and playful grin hinting at the corner of his lips. John chuckled a bit, before trying to think on his feet. Anything to get space between them.

"Maybe just a cuppa? I'm going to go...um...change clothes." He turned toward the small corridor that led to what he hoped was Molly's bedroom. A deep voice echoed softly by the woman's ear. John felt the hot, steady puffs of air as Sherlock whispered to him. 'No, _not_ him. Molly.'

"Don't you think you need some help with that?" He mumbled the question with a husky tone in his voice, causing John to jump out of the arms that had attempted to wrap around Molly's thin middle.

"Uh...um...no. I'm...I'm okay. I think I'm just going to get ready for bed. My head hurts. You just, um, stay here, and make me that tea. Please." Sherlock furrowed his brow, his eyes narrowing a bit, before he turned to move back to the kitchen. John took the opportunity to bolt into Molly's room, slamming the door behind him. He let out a deep sigh, relieved to be away from the consulting Casanova's love struck actions.

"Honestly, Sherlock Holmes. Who would have ever guessed that?" He muttered to himself. He made to move further into the room, and saw a pair of comfortable pyjamas laying on the edge of Molly's bed. It suddenly struck John that perhaps retreated to 'change clothes' had been a bad idea. The army doctor and veteran soldier was determined to keep Molly's dignity intact whilst he resided in her body. He may have been 'Three Continents Watson' at one time, but that certainly didn't mean he was a sleaze. So, blindly pulling off Molly's wool jumper, he moved to pick up the soft silk top. As it turns out, not looking was much more difficult than he'd thought it would be. A few accidental brushes of his hands against softer skin than his own had John stealing a second, a third, nearly a fourth glance down at Molly's prim figure.

He had to admit, she _was_ rather lovely. He also was glad that the world's biggest consulting idiot had finally caught on to that fact as well. He'd just rather _not_ discover how wise Sherlock had grown on the subject of the pathologist's anatomy.

A light knock at the door sounded, and John quickly finished pulling the light sleep trousers over the thin legs he was using, and made his way to sit on the bed.

"Come in!" He called, internally berating himself for sounding like a nervous wreck. The door swung open gently, and Sherlock carried two mugs of tea into the cozy room. He handed one to John, who quickly took it, taking a sip before the taller man could ask any sort of question. The tea was too hot, and too sweet for his own palate.

"I don't really like sugar in my tea...but thank you for making me some." He used Molly's sweet smile, hoping to throw Sherlock off the scent of his obvious nerves, as well as heal the detective's seemingly bruised ego. Sherlock nodded his head slightly, and turned toward the door.

"I'll go and fetch you some biscuits as well, then."

"Ta," John replied. Sherlock stopped dead in his tracks, and flung himself around to face John once more. The devilish twinkle in his eye had John worried, until the genius let out a loud chuckle.

"Ha! I knew it! Oh, brilliant! Oh, wait until I tell Mycroft. He didn't believe me, you know, that it would work. Temporary body-conscious displacement; they'll give me a knighthood for this...well, _try_." Sherlock seemed manic in his excitement, victoriously pacing back and forth in the small room. John sat by, slowly putting the puzzle pieces together. When it finally snapped into place, the picture created was one that he found incredibly disturbing, and had his face going red with anger.

"Wait...you! Oh my God, Sherlock! You could have killed us!" John shouted, no longer trying to keep Molly's gentle personality about.

"Oh please, John. The worst that would have happened is you would have experienced a bit of formaldehyde poisoning, mild nausea from the hallucinogens, and loss of consciousness. I did the math perfectly." Sherlock was definitely pleased with himself, which only served to fuel John's rage further.

"Do you hear yourself? You could have _poisoned _Molly!" It was this statement that wiped the clever smirk from Sherlock's face.

"Is she alright? What are some of the side effects? I should have...why didn't you tell... Have respiratory difficulties been a factor? Did she mention anything to you at all? Oh...oh shit." Sherlock's mind spewed out the several thoughts and worries at once, his pacing gait growing faster until John stepped in his way.

"She's fine. At least, I'm assuming she's fine. I haven't had any difficulties, other than the obvious discomfort of being in someone else's body!" Molly's voice cracked under the pressure of John's stressed shout. He balled up the slender hand he currently possessed, and moved to punch Sherlock's face. It hurt him more than the clearly amused detective.

"Come on, John. We must get you back to your body, and my pathologist back to hers," he said, motioning for John to follow him.

OoOo

"Soooo... how did you figure out this thing worked? I can guarantee you didn't know at first, or; if you did, we need to have a very serious conversation." John had been lecturing his friend for the entire ten minutes that they'd been in the cab. The genius level-man child had sulked as he listened to not one, but _two_ people scold his behavior.

"I'd first suspected that the switch was a success when we were all in the lab. Your vernacular is much more crude than Molly's. Plus, Molly never bosses anyone around, or asks for anything." John sighed, knowing he hadn't had a chance against his best friend's practiced skills.

"Also," Sherlock continued, "you don't take sugar in your tea, whereas Molly prefers hers to be sweetened beyond reasonable measure." John had to chuckle at that, secretly surprised that such a detail would remain 'relevant' for the man's brain.

"All the bloody time with the sugar in my tea. I really hate you sometimes, you know that?" John quipped.

"No, you don't."

OoOo

They had arrived at Baker Street, and found John's form nervously flitting about. Sherlock took a step closer, grabbing her by the wrist, and forcing Molly to glance up with startled eyes. However, surprise turned to rage as she saw the sheepish and slight remorseful grin on her detective's face.

"You knew this would happen?! Why, Sherlock? I thought I wouldn't ever get to...I... you're such an ass." It was an odd experience for John, watching his own eyes glaze over with salty tears. It was even weirder watching his 'sociopath' of a friend attempt to console him, or rather, Molly. He decided to step in, acting as a buffer between the two parties.

"Molly, believe me, I've given him a firm and numerous list of reasons why he's an ass, and we can kill him later...but first, what do you say we sort this out? Yea?" Sherlock nodded his head, half in appreciation for John's advice. He looked to the body that contained his Molly, and gave a hopeful smile. She finally acquiesced, letting out a heavy sigh, furrowing John's deep wrinkle in his forehead.

"Okay."

OoOo

The chemical had been injected nearly half an hour before John or Molly woke. It was Molly who woke first, and after a short quiz from Sherlock to ensure it was _truly _her, he let her know just how sorry he was, and how much he had missed her for the past twelve hours. John awoke shortly after, chuckling to himself as he watched the pathologist and detective sharing their mutual, and now public affection. He checked over himself, feeling his arms, legs, and chest. He was only too happy to find everything was _his_ and in order. John decided to leave the two alone, and made his way to the exit. It wasn't until the lab door had swung shut that he heard Molly coyly ask,

"So, who's a better kisser, John or me?" The sound of Sherlock's laughter echoed down the hall, and John quickly made his leave, deciding that he more than hoped it meant he had lost that title.

**The End.**

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Well, yay! It's finally complete! I hope you all enjoyed this story as much as I enjoyed writing it. Apologies that it took a bit longer than originally anticipated, but I hope the contents make up for it. :D Thanks again, everyone who has read this story, and special thanks to HanHan84, for providing such a wonderfully clever and fun prompt!

Love you all! Thank you ever so much!


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